It is generally known in the art to employ polycarbonate resins, which have excellent physical properties for molded and shaped articles but low thermoplasticity, with certain graft copolymers based on butadiene, acrylonitrile, and styrene to produce blends exhibiting thermoplastic properties (see, e.g., U.S. Pat. No. 3,130,177). These blends also may be less expensive than non-blended polycarbonate. The polycarbonate (PC) blends with acrylonitrile/butadiene/styrene (ABS) terpolymers are used in various applications. However, blends of this type can have problems with processibility, toughness, streaks, delamination, and low temperature performance.
It is also known that the impact strength of a high molecular weight polycarbonate can be improved by adding a combination of a methacrylate/acrylate copolymer and an olefin/alkyl acrylate copolymer (see, e.g., U.S. Pat. No. 4,260,693). In U.S. Pat. No. 4,390,657, the use of a multiphase composite interpolymer (see, e.g., U.S. Pat. No. 4,096,202) involving an methacrylate/acrylate copolymer with a small amount of a third crosslinking monomer and a graftlinking monomer, in the presence of a final rigid thermoplastic phase polymerized in the presence of these, is shown to improve the impact strength of a PC-ABS blend.
Modified PC-ABS blends with methylmethacrylate-butadiene-styrene (MBS) polymers to improve their impact strength have been disclosed (see, e.g., U.S. Pat. No. 4,696,972). Other impact modifiers include acrylonitrile/butadiene/styrene copolymers with high amounts of butadiene.
A PC-ABS blend having improved impact resistance can be achieved by the addition of an ethylene/alkyl acrylate ester copolymer or certain functionalized terpolymers thereof (see, e.g., WO2003/097743).
Copolymers comprising ethylene and alkyl acrylate or alkyl methacrylate monomers and terpolymers comprising ethylene, butyl acrylate, and glycidyl methacrylate have each been used as modifiers for toughening PC-ABS blends, but the composition obtained in either case can have delamination problems and streaks when used in an injection molding process. As a result, ethylene/alkyl(meth)acrylate copolymers, as PC-ABS modifiers, have problems when used in applications having a PC content of at least 50 weight %.
WO2005/042638 discloses PC-ABS blends modified with a blend of an ethylene/alkyl (meth)acrylate copolymer and an ethylene/butyl acrylate/glycidyl methacrylate terpolymer.
It is desirable to modify PC-ABS blends having greater than 50 weight % polycarbonate with a modifier that will improve at least one of the problem areas without detriment to other properties. For example, compositions with improved toughness, much better tensile properties and no delamination are desirable.